JP2894261B2 - Projection lens and liquid crystal projector using the projection lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection lens for enlarging and projecting an image projected on a panel onto a screen, and more particularly to a projection lens used for a liquid crystal projector or the like which requires high resolution. Further, the present invention relates to a liquid crystal projector using the projection lens.

[0002]

2. Description of the Related Art In a liquid crystal projector, a light beam emitted from a light source is reflected by a dichroic mirror into red (R).
The light is separated into three primary colors of green (G) and blue (B), and is incident on a liquid crystal panel corresponding to each color. The luminous flux transmitted through each liquid crystal panel is synthesized again by a dichroic mirror, and is enlarged and projected on a screen by a projection lens.
As a projection lens used in such a liquid crystal projector, a lens called a retrofocus in which a distance (back focus) between the projection lens and the liquid crystal panel is longer than a focal length is used. The reason why the back focus is necessary is to secure a space for disposing a dichroic mirror for color synthesis between the projection lens and the liquid crystal panel.
If the focal length is increased, wide-angle projection cannot be performed, and the projection distance must be increased to obtain a large screen. Therefore, a retrofocus lens with a large back focus and a small focal length of the projection lens Is used. In general, a retrofocus lens has a lens configuration in which the refractive power distribution of a concave lens and a convex lens is in order from the screen side.

[0003]

Generally, in a projection lens used for a liquid crystal projector or the like in which an image projected on a panel is enlarged and projected on a screen, an F number (lens or lens) representing the brightness of an optical system is used. It is desired that the lens configuration be made as small as possible to minimize aberrations such as distortion, astigmatism, and chromatic aberration of magnification over the entire projection screen. However, in a projection lens such as a retrofocus lens used in a conventional liquid crystal projector or the like, it is necessary to sufficiently correct aberrations such as distortion, astigmatism, and chromatic aberration to increase the resolution. However, there is a problem that the number of lenses increases and the cost increases. In addition, since the distortion is about 2 to 3% in each of the maximum images, for example, in a case where a plurality of liquid crystal projectors are arranged and an image projected from each is superimposed to obtain a brighter image, each of the projected images is projected. There is a problem that images to be reproduced cannot be completely overlapped.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and to reduce aberrations such as distortion, astigmatism, and chromatic aberration over the entire projected image with a configuration having a small number of lenses, and to increase the resolution. It is to provide a projection lens capable of. Still another object is to provide a liquid crystal projector using the projection lens.

[0005]

The projection lens according to the present invention comprises:
First to sixth lenses, each of which is a single lens, are sequentially arranged from the projection surface side. The first lens is a biconvex lens, and the second lens is a positive meniscus having a convex surface facing the projection surface side. Lens, the third lens is a negative meniscus lens having a convex surface facing the projection surface side, and the fourth and fifth lenses are integrally joined, and the negative meniscus lens having the convex surface facing the image surface side as a whole The sixth lens is a biconvex positive lens, and each lens has its refractive index, Abbe number with respect to d-line, and lens arrangement set so as to cancel aberrations generated in each lens, and the Abbe number is set inside. Set so that the lens becomes smaller
Have been.

[0006] Under such a premise, the first to sixth embodiments
The radius of curvature of each lens is represented by r1 to r11 from the projection surface side, and the lens thickness and air gap are d1 from the projection surface side.
To d10, the focal length of the projection lens is 10
In the case of 0 mm, the refractive indices n1 to n6 of the first to sixth lenses, Abbe numbers ν1 to ν6 for d-line, radii of curvature r1 to r11, lens thickness and air spacing d1 to d10 are given under the following conditions. It is characterized by having been done.

[0007]

[Table 2] A liquid crystal projector according to the present invention includes at least one of the above-described projection lenses, and a liquid crystal panel is disposed at a back focus position of the projection lens.

In this case, an optical member may be arranged between the projection lens and the liquid crystal panel.

<Operation> In the present invention configured as described above, the refractive index of the first to sixth lenses, the Abbe number with respect to the d-line, and the lens arrangement are set so as to cancel the aberrations occurring in each of the first to sixth lenses. Therefore, aberrations such as spherical aberration, distortion, and astigmatism are sufficiently corrected over the entire captured image. Further, in a lens configuration such as the present invention, it is experimentally possible to perform chromatic aberration correction more effectively in a state where the Abbe number of the first to sixth lenses is set to be smaller for the lens disposed on the inner side. Has been obtained.

In the liquid crystal projector of the present invention,
Since the projection lens having the above-described operation is used, for example, in a case where a plurality of liquid crystal projectors are arranged and an image projected from each is overlapped to obtain a brighter image, the image projected respectively is Can be completely overlapped.

[0011]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a structural view schematically showing a projection lens according to an embodiment of the present invention.

The projection lens of this embodiment has six single lenses, that is, lenses L1 to L1 arranged sequentially from the projection surface side.
L6. The lens L1 is a biconvex lens,
The lens L2 is a positive meniscus lens having a convex surface facing the projection surface, and the lens L3 is a negative meniscus lens having a convex surface facing the projection surface. The lenses 4 and 5 are integrally joined to form a negative meniscus lens having a convex surface facing the incident surface as a whole. The lens 6 is a biconvex positive lens. In the figure,
r1 to r11 are the radii of curvature of the lens surfaces of the lenses L1 to L6, n1 to n6 are the refractive indices of the lenses L1 to L6, d1 to d10
Indicates lens thickness and air gap.

In this projection lens, the focal length of the projection lens and the positive and negative aberrations occurring in the lenses L1 to L6.
According to the negative balance, the refractive index of each lens, the Abbe number for d-line, and the lens arrangement are determined. Here, the positive / negative balance of the aberration refers to, for example, the lens L1
If the lens surfaces L6 to L6 are the first to eleventh surfaces in order from the projection surface side, the first surface +0.73, the second surface +0.4
····, 5th surface -0.73, 6th surface -2.75, ····
The positive and negative balance of spherical aberration as described above, and the aberration is canceled by the balance.

In the projection lens having the above configuration,
For example, the refractive indices n1 to n6 of the lenses L1 to L6 and the Abbe numbers ν1 to ν6 for the d line (wavelength 587.6 nm) are given under the following conditions, and the focal length of the projection lens and the positive and negative aberrations of each lens are given. Depending on the balance of the lens L1
When the radius of curvature of L6, the lens thickness, and the air gap are determined, it is possible to favorably correct aberrations such as spherical aberration, astigmatism, distortion, and chromatic aberration over the entire projected image.

[0016]

[Table 3] Hereinafter, as a specific example, the focal length f is set to 100 mm.
Radius of curvature and lens thickness of each lens
The optimum value of the air gap is listed.

<Embodiment> The focal length f is 100 mm,
Member 4.0, back focus bf 69.8m
m and the maximum image height H is 20 mm, the lenses L1 to L
The optimum values of the radius of curvature of 6, lens thickness and air space are as follows.
The values are as shown in the table.

[0018]

[Table 4] In this case, spherical aberration, astigmatism, and distortion are
2 (a) to 2 (c). As can be seen from FIG.
By using the conditions in the above table, spherical aberration and astigmatism
Aberration and distortion are smaller.
Also, in the chromatic aberration correction, each lens
Lens with smaller Abbe number
In this state, a more effective correction is obtained
I have.

When the projection lens of the present invention described above is used.
FIG. 3 shows an example of the obtained liquid crystal projector.

In FIG . 3, reference numeral 100 denotes the configuration shown in FIG.
, A projection lens 101, a light source 101, and 102a to 102c
, 103 is a filter, 104a to 104d are dikes
Loic mirrors, 105a to 105c are liquid crystal panels
You.

A mirror is provided in the traveling direction of the light beam from the light source 100.
102a is arranged and reflected by the mirror 102a
Filter 103, dichroic mirror in the traveling direction of light beam
-104a, 102c, liquid crystal panel 105c, and
102d are sequentially arranged. Dichroic Mi
At the mirror 104a, R light is reflected and GB light is transmitted.
You. B light is reflected by the dichroic mirror 104b.
It is, the bulk G light permeability.

The light is reflected by the dichroic mirror 104a.
Mirror 102b is arranged in the traveling direction of the reflected light beam (R light)
And the traveling direction of the light flux reflected by the mirror 102b.
LCD panel 105a, dichroic mirror 104
c, 104d and the projection lens 100 are arranged. Da
The luminous flux (B) reflected by the ichroic mirror 104b
The liquid crystal panel 105b and the dichroic
The dichroic mirror 104c is disposed
The R light is transmitted through the back mirror 104c and the B light is
The luminous flux is radiated to synthesize these luminous fluxes.

The light beam (G reflected by the mirror 102c )
The dichroic mirror 104d
Is arranged on the dichroic mirror 104d.
RG from the dichroic mirror 104c
Light is transmitted, G light is reflected, and these light fluxes are synthesized.
Will be

In the above liquid crystal projector, each liquid crystal panel
Panels 105 to 105c are backfountains of the projection lens 100.
Liquid crystal panels 105 to 1
R, B, and G images projected on 05c are not shown
Is magnified and projected on the screen.

The above-mentioned liquid crystal projector has three
R, B, and G projected on a transmissive LCD panel
The image is color-composited, and the color-combined video is projected into one
Although it is configured to project with a lens, for example, three
R, B, and G images projected on a reflective LCD panel
An image is projected by three projection lenses.
Is also good.

[0026]

The present invention is configured as described above.
Therefore, the following effects can be obtained.

According to the first aspect of the present invention, the distortion correction
Aberrations such as difference, astigmatism, and chromatic aberration are sufficiently corrected.
To provide a high-resolution projection lens over the entire projection screen.
There is an effect that can be provided. Furthermore, 6 in 5 groups
It is possible to reduce the number of lenses
There is an effect that can be.

According to the second and third aspects of the present invention,
Since a projection lens having the function as described above is used,
In addition to providing high-resolution images,
Place the projectors and overlay the images projected from each
There is an effect that a brighter image can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a projection lens according to an embodiment of the present invention.

2A and 2B are diagrams showing aberrations in the projection lens shown in FIG. 1, wherein FIG. 2A shows spherical aberration, FIG. 2B shows astigmatism, and FIG. 2C shows distortion.

FIG. 3 is a configuration diagram schematically showing a liquid crystal projector to which the projection lens shown in FIG. 1 is applied.

[Explanation of symbols]

 L1 to L6 Lens d1 to d10 Lens thickness and air spacing n1 to n11 Refractive index r1 to r11 Radius of curvature 100 Projection lens 101 Light source 102a to 102c Mirror 103 Filter 104a to 104d Dichroic mirror 105a to 105c Liquid crystal panel

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (3)

(57) [Claims] 1. A first lens to a sixth lens, each of which is a single lens, are sequentially arranged from a projection surface side. The first lens is a biconvex lens, and the second lens has a convex surface on a projection surface side. A positive meniscus lens, the third lens is a negative meniscus lens having a convex surface facing the projection surface side, and the fourth and fifth lenses are integrally joined together, with the convex surface facing the image surface side as a whole. The negative meniscus lens, the sixth lens is a biconvex positive lens, and each lens has its refractive index, Abbe number for d-line, and lens arrangement set so as to cancel aberrations generated in each lens. The Abbe number is smaller for the inner lens, and the radius of curvature of each of the first to sixth lenses is projected.
It is expressed by r1 to r11 from the surface side.
When represented by d1 to d10 from the projection surface side, a projection lens
When the focal length of the lens is 100 mm,
Refractive index n1 to n6 of lens No. 6, Abbe number for d-line
ν1 to ν6, radius of curvature r1 to r11, lens thickness and air
A projection lens, wherein the distances d1 to d10 are given under the following conditions . [Table 1] 2. The projection lens according to claim 1,
And one at the back focus position of the projection lens.
A liquid crystal projector with a liquid crystal panel. 3. The liquid crystal projector according to claim 2,
Between the projection lens and the liquid crystal panel.
Liquid crystal projector wherein members are arranged
-